Table of ContentsView AllTable of ContentsHow Does Plan B Work?Possible Side EffectsFrequently Asked Questions
Table of ContentsView All
View All
Table of Contents
How Does Plan B Work?
Possible Side Effects
Frequently Asked Questions
Plan B One-Step, often called “Plan B,” is an emergency contraceptive (EC). It is also called “the morning-after pill.”
Plan B contains a synthetic hormone called levonorgestrel, which can prevent ovulation, or the release of an egg. This is how Plan B works to prevent pregnancy.
Emergency contraceptives like Plan B One-Step prevent pregnancy afterbirth control failureor unprotected sex. Generic forms of Plan B includeMy Way,Take Action, andNext Choice One Dose.
Justin Sullivan / Getty Images
This article looks at what the research says about how Plan B works. It also discusses some of the side effects you may experience when taking Plan B.
Emergency contraception is safe and effective. Still, Plan B iscontroversial. Much of the debate is based on a misunderstanding about how Plan B works.
Some people believe Plan B prevents a fertilized egg from implanting in the lining of the uterus. But research does not support this theory about how Plan B works, though.
Studies have shown that Plan B does not decrease the pregnancy rate when taken after ovulation.This suggests it may not interfere with fertilization or implantation, just ovulation.
1:38All About Plan B One-Step Emergency Contraception
1:38
All About Plan B One-Step Emergency Contraception
Most research suggests that Plan B does not cause changes in theendometrium, or lining of the uterus.Because of this, researchers have concluded it cannot prevent implantation of a fertilized egg.
The most common side effect of Plan B is a change in your period. Your period may come sooner or later than expected. You may also have heavier or lighter bleeding or spotting before your period.
Otherside effects of Plan Bmay include:
Plan B is not meant to be used as your primary method of birth control. Though there don’t seem to be any health risks or a reduction in effectiveness if you use Plan B frequently, it can cause unwanted side effects. This can include irregular or unpredictable periods.
Plan B is also less effective than long-term birth control, so if you use it often, you should talk to your healthcare provider about other, more effective ways to prevent pregnancy.
Summary
Because it is less effective than other types of birth control, Plan B is not meant to be used as a primary form of birth control.
It takes about 1.7 hours for the levonorgestrel in Plan B to reach peak levels in your blood.After this, it will delay ovulation for a few days. Plan B is most effective within 72 hours of unprotected sex.
You can buy Plan B over-the-counter at many major retailers. It can also be found in pharmacies. You do not need a prescription, and you do not need to show ID to purchase Plan B.
If you haven’t already ovulated, Plan B will work to prevent the release of an egg. If you take it after ovulation, it won’t work. This is why healthcare providers recommend taking Plan B as soon as possible after unprotected sex.
Correction - June 16, 2023: This article was updated to reflect the FDA’s updated stance that Plan B does not affect implantation and is, therefore, not an abortion drug.
4 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Food and Drug Administration.Plan B One-Step (1.5 mg levonorgestrel) information.Gemzell-Danielsson K, Berger C, Lalitkumar PGL.Emergency contraception — mechanisms of action.Contraception. 2013;87(3):300-308. doi:10.1016/j.contraception.2012.08.021Novikovaa N, Weisberg E, Stanczyk FZ, Croxattod HB, Fraser IS.Effectiveness of levonorgestrel emergency contraception given before or after ovulation — a pilot study.Contraception. 2007;75:112-118. doi:10.1016/j.contraception.2006.08.015Matyanga CM, Dzingirai B.Clinical pharmacology of hormonal emergency contraceptive pills.Int J Reprod Med. 2018;2018. doi:10.1155/2018/2785839
4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Food and Drug Administration.Plan B One-Step (1.5 mg levonorgestrel) information.Gemzell-Danielsson K, Berger C, Lalitkumar PGL.Emergency contraception — mechanisms of action.Contraception. 2013;87(3):300-308. doi:10.1016/j.contraception.2012.08.021Novikovaa N, Weisberg E, Stanczyk FZ, Croxattod HB, Fraser IS.Effectiveness of levonorgestrel emergency contraception given before or after ovulation — a pilot study.Contraception. 2007;75:112-118. doi:10.1016/j.contraception.2006.08.015Matyanga CM, Dzingirai B.Clinical pharmacology of hormonal emergency contraceptive pills.Int J Reprod Med. 2018;2018. doi:10.1155/2018/2785839
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Food and Drug Administration.Plan B One-Step (1.5 mg levonorgestrel) information.Gemzell-Danielsson K, Berger C, Lalitkumar PGL.Emergency contraception — mechanisms of action.Contraception. 2013;87(3):300-308. doi:10.1016/j.contraception.2012.08.021Novikovaa N, Weisberg E, Stanczyk FZ, Croxattod HB, Fraser IS.Effectiveness of levonorgestrel emergency contraception given before or after ovulation — a pilot study.Contraception. 2007;75:112-118. doi:10.1016/j.contraception.2006.08.015Matyanga CM, Dzingirai B.Clinical pharmacology of hormonal emergency contraceptive pills.Int J Reprod Med. 2018;2018. doi:10.1155/2018/2785839
Food and Drug Administration.Plan B One-Step (1.5 mg levonorgestrel) information.
Gemzell-Danielsson K, Berger C, Lalitkumar PGL.Emergency contraception — mechanisms of action.Contraception. 2013;87(3):300-308. doi:10.1016/j.contraception.2012.08.021
Novikovaa N, Weisberg E, Stanczyk FZ, Croxattod HB, Fraser IS.Effectiveness of levonorgestrel emergency contraception given before or after ovulation — a pilot study.Contraception. 2007;75:112-118. doi:10.1016/j.contraception.2006.08.015
Matyanga CM, Dzingirai B.Clinical pharmacology of hormonal emergency contraceptive pills.Int J Reprod Med. 2018;2018. doi:10.1155/2018/2785839
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